1. Field of the Invention
The present invention relates to a steel-plate-reinforcement resin composition, a steel plate reinforcing sheet, and a reinforcing method of a steel plate. More particularly, the present invention relates to a steel-plate-reinforcement resin composition, adhesively bonded to a steel plate used in a variety of industrial machines such as transportation machines, for reinforcing the steel plate, a steel plate reinforcing sheet, and a method of reinforcing the steel plate using the steel plate reinforcing sheet.
2. Description of the Prior Art
In general, a steel plate for a shell of an automotive vehicle is manufactured in the form of a thin sheet having a thickness generally in the range of 0.6 mm to 0.8 mm, for reduction in weight of a vehicle body. Accordingly, the steel plate is reinforced by adhesively bonding a steel plate reinforcing sheet to the inside of the steel plate.
Epoxy resin composition in the form of a sheet is known as the steel plate reinforcing sheet. For example, JP Laid-open (Unexamined) Patent Publication No. 2002-283526 proposes a thermally curable adhesive sheet for reinforcing a thin steel plate having a structure wherein uncured adhesive layers of epoxy resin composition having adhesiveness at room temperature and containing a thermally decomposable foaming agent are laminated in layers on a base material layer of uncured epoxy resin composition.
When the epoxy resin composition is formed in a sheet form, a liquid epoxy resin and a solid epoxy resin are mixed in a proportion so that the epoxy resin composition in the form of a sheet develops adhesiveness at about room temperature.
However, it is very difficult to satisfy both of adhesiveness and handleability of the epoxy resin composition in the form of a sheet at about room temperature, e.g., in a relatively wide temperature range of 5-35° C.
Allowing the epoxy resin composition to develop good adhesiveness at low temperature of about 5° C. requires a further increased ratio of the liquid epoxy resin, while however, such a further increased ratio of the liquid epoxy resin makes the epoxy resin composition to too sticky paste at high temperature of about 40° C., making it hard to strip the epoxy resin composition in the form of the sheet from a separator and thus causing inconvenience to the handleability.
On the other hand, allowing the epoxy resin composition to develop good adhesiveness at high temperature of about 40° C. requires an increased ratio of the solid epoxy resin, while however, such an increased ratio of the solid epoxy resin produces the disadvantage that the epoxy resin composition does not develop the good adhesiveness at low temperature of about 5° C.